Apoptosis in fetal nucleated erythrocytes circulating in maternal blood

The purpose of this study was to determine if apoptosis occurs in fetal cel ls that have crossed into the maternal circulation, which would potentially explain the difference between the number of intact fetal cells and the am ount of fetal DNA detectable in maternal plasma. We how-sorted fetal nuclea ted erythrocytes (FNRBCs) using antibody to the gamma chain of fetal haemog lobin and confirmed them to be fetal in origin by FISH analysis using chrom osome-specific probes. Fetal cells were then analysed microscopically for t he presence of terminal UdTP nuclear end labelling (TUNEL) staining. Apopto tic change was observed in 42.7% of fetal NRBCs (106/246) and 3.5% of mater nal cells (29/818). Results of this study indicate that a significant numbe r of fetal cells in maternal blood are undergoing apoptosis at the time of sampling. Apoptosis may be one mechanism by which fetal cells are cleared b y the maternal circulation. Copyright (C) 2000 John Wiley & Sons, Ltd.